Narcolepsy is a sleep disorder that causes symptoms including excessive daytime sleepiness and cataplexy – sudden attacks of muscle weakness that may be triggered by strong emotion. While narcolepsy is rare in the general population, it is more common in people with certain health conditions. These conditions may be related to narcolepsy in different ways. When someone has more than one health condition at the same time, the conditions are known as comorbidities.
Understanding common comorbidities of narcolepsy can help people recognize symptoms and talk to their doctors about treatment. Treating comorbidities may improve quality of life.
Some medications can cause dangerous interactions with narcolepsy treatments. Always make sure your health care provider is aware of every medication you are taking for every condition, whether it is available over the counter or by prescription, including any vitamins or herbal supplements.
People with narcolepsy have an increased risk for experiencing other sleep disorders as well.
Obstructive sleep apnea (OSA) is a sleep disorder that causes a person to stop breathing intermittently during sleep. Approximately 3 percent to 7 percent of the population has OSA.2 Like narcolepsy, OSA is associated with excessive daytime sleepiness. OSA is common in people with narcolepsy. In one study of 133 people with narcolepsy, 33 participants were also diagnosed with sleep apnea.
One problem arising from the frequent comorbidity of OSA is delayed diagnosis of narcolepsy. OSA can be diagnosed from an overnight sleep study (polysomnography), and many doctors assume that excessive sleepiness is due to sleep apnea alone. They may treat sleep apnea without proceeding to diagnostic testing for narcolepsy. Unfortunately, most people with excessive daytime sleepiness caused by narcolepsy do not improve with continuous positive airway pressure (CPAP), the most common treatment for obstructive sleep apnea.
About 5 percent of the U.S. population has restless legs syndrome (RLS), a neurological sleep-related movement disorder that causes uncomfortable sensations in the legs that become worse with rest or at night. However, between 15 percent and 20 percent of people with narcolepsy experience RLS. In about half of RLS cases, restless legs syndrome runs in families.
RLS can cause disrupted sleep and make it difficult to nap. Some common treatments for restless legs syndrome can cause excessive daytime sleepiness as a side effect.
Also known as periodic limb movements disorder (PLMD), periodic limb movement syndrome (PLMS) is another sleep-related movement disorder that can disrupt sleep and contribute to daytime sleepiness. PLMS causes rapid, repetitive twitching movements of the limbs during sleep. PLMS may occur with or without RLS in people with narcolepsy.
The Burden of Narcolepsy Disease (BOND) study included 9,312 American adults diagnosed with narcolepsy. Published in 2013, the results of the BOND study found a high rate of psychiatric comorbidities compared with rates seen in people without narcolepsy. These comorbidities included mood disorders such as depressive and bipolar disorders, anxiety and attention disorders, and psychotic disorders including schizophrenia.
Accumulating research shows a relationship between sleep — especially REM sleep — and the regulation of emotions. Sleep is thought to help us protect and regulate the process of forming emotional memories and to contribute to healthy emotional reactivity. Sleep loss, on the contrary, makes it harder to modulate emotion.
Treatments for psychiatric disorders may make it more difficult for doctors to diagnose narcolepsy. Some treatments for psychiatric disorders, such as antipsychotic medication, may worsen narcolepsy symptoms. Stimulants prescribed for narcolepsy may also worsen psychotic symptoms.
In general, people with chronic health conditions are at higher risk for depression. In one study published in 2017, researchers surveyed 1,699 people who reported having narcolepsy. Depression was the most common comorbidity reported. According to the BOND study, people with narcolepsy were 22.8 percent more likely to develop depressive disorders compared with healthy controls.
The results of the BOND study showed that adults with narcolepsy are 13 percent more likely to have anxiety disorders than those without narcolepsy. People with narcolepsy may experience panic attacks or social anxiety related to fear of having a sleep attack in public or losing control of their bodies.
Among participants in the BOND study, those with narcolepsy had a 6.2 percent higher chance of having bipolar disorder. Formerly known as manic depression, bipolar disorder involves swings of mood, energy, and concentration that may be “up” or “down.” In at least one person with narcolepsy, treatment for narcolepsy (specifically Modafinil and Venlafaxine) exacerbated manic episodes.
Findings of the BOND study included a 2.5 percent higher risk for people with narcolepsy to have schizophrenia. While both schizophrenia and narcolepsy can cause hallucinations, the hallucinations experienced in schizophrenia tend to be auditory in nature. The hypnagogic hallucinations (hallucinations that occur when falling asleep) in narcolepsy are usually visual. In at least one case, a child with narcolepsy type 1 was misdiagnosed with schizophrenia.
People with narcolepsy have a higher risk for developing metabolic disorders, which relate to energy, weight, and sexual development.
Overweight and obesity are common in people with narcolepsy, with adults weighing on average 15 percent to 20 percent more than those without narcolepsy. Children who develop narcolepsy often gain significant weight in the months following the emergence of symptoms. Obesity was nearly twice as likely in children with narcolepsy — 74 percent compared with 36 percent in the general population. A 2007 study including 13 people with narcolepsy found that those with type 1 narcolepsy (narcolepsy with cataplexy) had a lower metabolism and tended to eat less than people without narcolepsy. The researchers theorized that the changes in metabolism may be connected to low levels of hypocretin (also referred to as orexin), a brain chemical connected with the cause of narcolepsy.
The development of narcolepsy in childhood is strongly associated with precocious puberty and obesity. (Precocious puberty is defined as puberty starting before age 8 in girls and age 9 in boys.) In an Italian study published in 2013, researchers evaluated 42 children with narcolepsy. The rate of precocious puberty among participants was 17 percent, almost 1,000 times higher than the rate in the general population. The researchers concluded that narcolepsy in children is likely related to dysfunction in the hypothalamus, the region of the brain where hypocretin is produced, and its relationship to the production of hormones that mediate puberty and metabolism.
According to the Diabetes Council, 33 percent of people with type 2 diabetes (also called diabetes mellitus) have disturbed sleep that may include restless legs syndrome or periodic limb movement syndrome. Sleep disruptions in diabetes grow more severe if hyperglycemia (high blood glucose) is poorly controlled. Sleep deprivation also seems to contribute to increasing insulin resistance.
One theory suggests that hypocretin, the chemical deficient in people with narcolepsy type 1, has a protective effect against diabetes. Thus, the risk for developing diabetes rises in people with narcolepsy.